1Historical biogeography traditionallydeals with relationships among species,genera, and higher taxonomic groupsand the areas they occupyPhylogeography — Historical Biogeographyof the SpeciesPhylogeography — Historical Biogeographyof the SpeciesDue to advances in DNA sequencing andfingerprinting methods, historicalbiogeography has recently begun tointegrate relationships of populationswithin species and the areas they occupyHistorical biogeography traditionallydeals with relationships among species,genera, and higher taxonomic groupsand the areas they occupyPhylogeography — Historical Biogeographyof the SpeciesJohn Avise, animal geneticist at University of Georgia, coined the termed“phylogeography” to describe “the history and formation of species” from ageographical perspectivePhylogeography — Historical Biogeographyof the SpeciesThe classic phylogeographicanalysis by Avise and his studentsinvolved the identification of astrong geographical signal withinspecies separating populationsfrom the Atlantic seacoast from theGulf of Mexico seacoast.The presence of two quite distinctgenotypes within all theseunrelated species has beenexplained by Pleistocene glacialand inter-glacial events2Phylogeography — Historical Biogeographyof the SpeciesOne of the most debated, and still unresolved, issues inphylogeography is the geographical origin of Homosapiens - the “Eve hypothesis” as maternally inheritedmitochondrial DNA (mtDNA) is often usedPhylogeography — Historical Biogeographyof the SpeciesThe “out-of-Africa” scenario is often supported - asshown here - and is consistent with the fossil record.However, different ways of analyzing DNA support an“out-of-Asia” scenario as well.Phylogeography — Historical Biogeographyof the SpeciesSteps in a phylogeographic study1. Sample populations widely acrossgeographical range of species3. Identify and quantify genotypes foreach population [haplotypes if cpDNAor mtDNA]2. Sample multiple individuals fromeach population to access levels ofvariation in cpDNA, mtDNA, or nucleargenesMap of the populations and distribution ofhaplotypes of Cedrela odorata (Spanish cedar)across Mesoamerica (Cavers et al. 2003)Phylogeography — Historical Biogeographyof the SpeciesSteps in a phylogeographic study4. Construct minimum spanning tree forthe haplotypes5. Overlay geographical distributionsonto the tree (or use Nested CladeAnalysis in complicated studies)Minimum spanning tree of five haplotypes andtheir geographic locations for Cedrela odorata(Spanish cedar) (Cavers et al. 2003)3Phylogeography — Historical Biogeographyof the SpeciesExample 1: Cryptic invasion of a non-native genotype of Phragmites australis(common reed) into North America (Saltonstall 2002)Native population in Great Lakes Invasive population in Great LakesPhylogeography — Historical Biogeographyof the SpeciesMinimum spanning tree for all genotypesEurope, Australasia,Africa, South AmericaNorth AmericanInvasive formNote that the native NorthAmerican genotypes are closelyrelated and they are unrelated tothe invasive form from the OldWorldPhylogeography — Historical Biogeographyof the SpeciesGenotyping of common reedfrom herbarium specimensprior to 1910 indicates thewidespread presence of 11native genotypes and 1southern genotype also seenin South America and AsiaPhylogeography — Historical Biogeographyof the SpeciesA few populations scatteredfrom Connecticut toMaryland prior to 1910 alsoexhibited the invasivegenotypeGenotyping of common reedfrom herbarium specimensprior to 1910 indicates thewidespread presence of 11native genotypes and 1southern genotype also seenin South America and Asia4Phylogeography — Historical Biogeographyof the SpeciesGenotyping of common reedfrom modern populations(both herbarium specimensafter 1960 and extantpopulations) indicates thesame distributions ofgenotypesPhylogeography — Historical Biogeographyof the SpeciesHowever, the invasivegenotype has dramaticallyspread across NorthAmerica since 1910Genotyping of common reedfrom modern populations(both herbarium specimensafter 1960 and extantpopulations) indicates thesame distributions ofgenotypesPhylogeography — Historical Biogeographyof the SpeciesThe “invasive” nature of theintroduced common reed ismore dramatically seen inthe time sequence ofgenotyping of pre-1900 tomodern populationsThe native North Americangenotypes are systematicallyreplaced by the invasiveform along the easternseaboard of Connecticut,Rhode Island, andMassachusettsPhylogeography — Historical Biogeographyof the SpeciesExample 2: History of the North Atlantic during the Pleistocene - differentiationin refugia (nunataks) or recent (Holocene) migration? (Brochmann et al. 2003)5Phylogeography — Historical Biogeographyof the SpeciesExample 2: History of the North Atlantic during the Pleistocene - differentiationin refugia (nunataks) or recent (Holocene) migration? (Brochmann et al. 2003)Phylogeography — Historical Biogeographyof the SpeciesNodding saxifrage, Saxifraga cernua1. North Atlantic populations do not showendemic genotypes2. Migration of several genotypes into (mixed)populations of North Atlantic regionsPhylogeography — Historical Biogeographyof the SpeciesLevels of species endemism in the NorthAtlantic - black pie sections indicate proportionof endemism3. Lack of endemic genotypes issupported by the general lack of endemicspecies in the glaciated North Atlanticregion. Genotype and species endemism,however, is high in “refugia” south ofglaciated